1. Field of the Invention
A device suitable for supplying a gaseous fuel to an internal combustion engine, as well as an evaporator, a metering device, a processor and a pressure regulating unit suitable for use in such a device.
2. Description of Related Art
The invention relates to a device suitable for supplying a gaseous fuel to an internal combustion engine comprising combustion chambers, which device is provided with an evaporator and with a metering device, said metering device on an inlet side being in communication with an evaporating chamber disposed within said evaporator, and on an outlet side being provided with a main pipe, said main pipe after said metering device branching into a number of pipes connected to the individual combustion chambers.
The invention furthermore relates to an evaporator, a metering device, a processor and a pressure regulating unit suitable for use in such a device.
From NL-8600611 such a device is known with a pressure modulator 23 located in the main pipe. The main pipe is connected to a branching device 29 in which the main pipe branches in a number of pipes 30 connected to the individual combustion chambers. The function of the pressure modulator 23 is to prevent that the pressure fluctuations in the inlet manifold influence the stability of the pressure controller/evaporator. Hereby deviations between the desired total gas flow and the actual total gas flow are prevented. Such variations could obviously occur as a result of variation in the pressure line.
The systems as described in NL-A-8600611 will, however., suffer from a poor distribution over the various cylinders as no specific measures are taken in the distribution lines and as a result of differences in the flow resistances of the individual pipes and of dynamic pressure differences in the inlet manifold.
The object of the invention is to provide a relatively simple device, by means of which gas can be supplied to an internal combustion engine in a metered manner whereby an optimalisation of the equal distribution of the total gas flow over the different cylinders of the combustion engine is obtained.
With the device according to the invention this objective is accomplished in that each pipe is provided with a fixed predetermined local/constriction, across which at least 85% of the pressure drop from the division of the main pipe into the individual pipes to the combustion chambers takes place, whereby the differences in the flow resistances of the local constrictions of the individual pipes are 5% at most.
Dynamic pressure variations which occur in the inlet manifold near the combustion chambers and which depend inter alia on the number of revolutions and the load and the location of each combustion chamber cannot penetrate into the pipes of the device as a result of the damping effect of the local constrictions. Differences in the distribution of the gas flow, which will occur in the device known from the aforesaid Dutch patent application as a result of this disturbance, are practically fully adjusted by the local constrictions, therefore. In addition to that the influence of variations in the length and the curvature of the pipes between the main pipe and the combustion chamber has become negligibly small.
Because the gas supply is distributed precisely proportionally over the various combustion chambers, the exhaust gases of the various combustion chambers will have substantially the same composition.
It is noted that with a device disclosed in Dutch Patent Application NL-A-9002862 gas in liquid or gaseous form is evaporated in the evaporator and then metered and distributed over the various combustion chambers of the internal combustion engine by means of the metering device. The metering device is to this end provided with a number of passages, which number corresponds with the number of combustion chambers. The passages need to be manufactured with relatively great precision in order to obtain a proper metering as well as a proper distribution. A drawback of such a device is that the metering device is relatively complicated as a result of this. In addition to that the device is provided with a number of pressure regulating units, which number corresponds with the number of combustion chambers, which makes the device relatively costly.
It is furthermore noted that from U.S. Pat. No. 3,799,124 a device is known wherein the flow resistance of a pipe can be changed, for example by means of an adjusting screw. This device has a number of serious drawbacks In practice it is not possible to realize a proper adjustment for each individual combustion chamber. The air/fuel proportion is not measured individually for each combustion chamber.
Thus there is no feedback information with regard to the adjustment of the adjusting screw and the result achieved therewith. Furthermore the adjusting of the various adjusting screws is a relatively time-consuming activity. With the known device the flow ratio of the pipe is changed by means of the adjusting screw, in such a manner that differences in the length and curvature of the pipes are adjusted for. From the aforesaid US patent it is not known, however, to adjust for a comparatively more important aspect, namely the dynamic pressure variations in the inlet manifold at the combustion chambers.
It is noted that U.S. Pat. No. 4,386,593 describes a device with adjustable valves 30 in each hose. However, as has been indicated above with respect to U.S. Pat. No. 3,799,124, in practise it will hardly be possible to realise an adjustment which meets the requirements that are set by the latest regulations with respect to emission. Furthermore such adjustment is only possible with special test equipment and is very time consuming.